This invention relates to semiconductor diode devices, and more specifically relates to a novel process for the manufacture of a fast recovery diode having soft turn-off characterisics.
It is well known that diffusion of gold into a semiconductor device will reduce the minority carrier lifetime in the device, thereby to make the turn-off time or recovery time of the diode much faster than in the absence of the gold. Gold atoms, however, have the property of diffusing very uniformly into and through the wafer so that the diode will turn off with a characteristic known as "hard turn-off" wherein the circuit containing the diode will experience high frequency oscillations during the turn-off time which can adversely affect the circuit characteristics.
It would be very desirable to construct a diode device with a fast recovery characteristic where, however, the turn-off is a soft turn-off rather than a hard turn-off so that the diode will stop conducting without producing adverse high peak voltage oscillations in the circuit containing the diode.